1. Field of the Invention
The present invention relates generally to analog recording and playback systems, and specifically, to a single or dual message, multilevel analog signal recording and playback system.
2. Background Information
Multilevel analog signal recording and playback devices have found numerous signal processing applications that require a low-cost, low power consumption, and compact solution. In these applications, analog techniques are preferable to digital techniques because a complete single-chip solution is possible with analog integrated circuits, enabling lower overall system cost for a given functionality or application.
One prior art single chip device for analog signal recording and playback is the ISD 1400 series manufactured by Information Storage Devices, of San Jose, Calif. The ISD 1400 series system is a single/multi message multilevel analog signal Recording and playback system. It has external addressing capability and special end of message (EOM) markers. Writing multiple messages requires the device to selectively clear rows before recording, which, in turn, requires additional pins and internal circuits.
Pending U.S. patent application Ser. No. 08/912,590, entitled "A Single Message Multilevel Analog Signal Recording and Playback System" filed Aug. 18, 1997, and assigned to the assignee of the present invention discloses a system with selectable duration capability.
The ISD 2500 series system enables functionality similar to the ISD 1400 series system with the additional ability to accept external signals as auxiliary inputs. However, it cannot perform a mix in function.
The present invention is an improvement of the aforementioned systems. In a voice application, the present invention offers (1) a single or multiple storage segments including a security feature to prevent overwriting of one or more segments; (2) an auxiliary input/mix in feature; (3) a microphone bias feature; (4) external selectable duration capability; and (5) lower system cost.